This invention relates to an air admittance valve to be connected to a sanitary waste pipe system in order to protect the water traps in the system and to prevent communication between waste pipes or sewers systems with surrounding atmosphere, said valve opens automatically to admit outside atmospheric air into the pipe system upon presence of a pressure drop within said pipe system.
A building drainage and vent system involves, in normal operating conditions, the establishment of an induced air flow within the vertical stacks of the system due to the unsteady water downfall generated by any appliance discharge. In order to protect the habitable space against contaminated odours, each appliance is normally protected by a water trap seal. Variation due to water downfall within the drainage system, generates occasional variations in air pressure that are often capable of disturbing these water trap seals either by siphonage due to a sudden under-pressure in the system or as a result of back pressures following air path closures by water surcharge.
Specially designed air admittance valves have been introduced to avoid said inconveniences and also offers the possibility of avoiding the necessity to vent the waste pipe system outside the roof of the building as said valves only open in response to sub-atmospheric pressure conditions in the waste pipe system.
Preferably, said valves are designed to assure a maximum possible air inlet flow from the air inlet of the valve to the waste pipe system while passing through the temporary opened valve membrane.
The U.S. Pat. No. 4,232,706, in the name of the applicant, discloses an automatic valve device in which a vertical tube, constituting the body of the valve, comprises at its upper end a constriction in the form of a Venturi which co-operates with a cover so as to form a peripheral air inlet provided with an annular valve member situated at the exterior of the constriction and which can be tilted when a negative pressure occurs in the pipes while permitting the fresh air to penetrate into the vertical waste water pipe and which, when the pressure is equilibrated or when there is overpressure, occupies a closed position in which the escape of contaminated air is prevented.
Said valve comprises an annular peripheral opening which distributes the air inlet, in case of lifting of the annular valve member, towards the vertical tube in connection with the waste pipe. Although this device gives generally very good results with an increased air inlet capacity due to the venturi shaped tube, it may happen, in particular circumstances that some turbulence may occur between the annular air inlet opening and the passage to the waste pipe. Said turbulence may occur when all of the air flow coming from the outer diameter of the annular valve member, in lifted position, is forced to be concentrated into a central tube portion of the pipe system having a smaller diameter and generally a smaller section than the overall annular valve section and will reduce, in some extend, the air inlet capacity.
In valves of this kind, the circular or annular valve member is generally resting on two concentric valve seats having each a circular sealing surface. In case of deformation or distortion of the valve member, problems could occur with the necessary airtight closure of said valve member with at least one of the two sealing surfaces.
An other kind of air admittance valve is disclosed in the parent document CH 201 565. This valve contains two diametrically opposed air inlet openings alternating with two diametrically opposed peripheral grooves connecting the upper surface of a circular disc shaped valve member with the waste pipe system. The air flow distribution in said valve is very limited, especially through the two narrow grooves, so that this kind of valve only can be used for one single sanitary appliance.
Patent document EP 0 409 506 discloses a valve device in which an annular peripheral air inlet is in communication with the lower face of an disc shaped valve member through one single radial passage. This passage disturbs the air flow towards the waste pipe system upon opening of the valve member. Obviously, the bad distribution of the air flow passages will create important turbulence in the air inlet and have a negative effect on the air inlet capacity of the valve.
A first object of the invention is to provide an automatic air admittance valve avoiding as much as possible the air turbulence within the valve by providing a optimum distribution in the vicinity of the valve function elements between the air inlet openings and the passages towards the waste pipe.
A second object of the invention is to provide a well balanced valve member shape and corresponding valve seat opening, allowing an optimum air distribution within the valve and providing a maximum lifting power to the valve member, the valve seat having only one sealing surface reducing the possible leakage problems of the valve member in closed position.
A third object of the invention is to provide the interior surface of the valve body with a plurality of means to improve the evacuation and collection of condensed water and to divert it into the waste pipe.
A fourth object of the invention is to incorporate grid netting immediately in the moulding of the valve housing, both in the air inlet openings and in the passages to the waste pipe, some of the grid elements being provided with enlarged portions in order to support the valve member in case of overpressure or fire in the waste pipe system.
A fifth object of the invention is to provide an air admittance valve for sanitary waste pipe systems which is easy to manufacture comprising only three components, each of them being directly obtain ed by a moulding process.
The above objects are achieved in accordance with the to principles of the present invention which are described more particularly in the annexed set of claims.
Numerous characteristics, advantages and features of the invention will appear from the following description of embodiments of the valve according to the invention and in which reference is made to drawings in which: